Congestion control method and aparatus for wireless networks

Abstract

A wireless terminal comprises a communications interface and a congestion controller. The communications interface communicates over a radio interface with a base station. The congestion controller, upon occurrence of a congestion indication, reduces uplink transmission power of the wireless terminal by lowering a transport format combination for use by the wireless terminal for transmitting an enhanced dedicated uplink channel (E-DCH) over the radio interface to the base station. In an example embodiment and mode, the congestion controller performs an expedited transport format combination reduction procedure which is distinct from Dedicated Physical Control Channel (DPCCH) power reduction based on a command received in a closed loop power control procedure, e.g., on a Fractional-DPCH (F-DPCH) channel.

What is claimed is:  
     
       1. A wireless terminal comprising:
 a communications interface configured to communicate over a radio interface with a base station; 
 a congestion controller configured, upon occurrence of a congestion indication, to reduce uplink transmission power of the wireless terminal by performing an expedited transport format combination reduction procedure which comprises lowering a transport format combination for use by the wireless terminal for transmitting an enhanced dedicated uplink channel (E-DCH) over the radio interface to the base station; 
 wherein:
 the expedited transport format combination reduction procedure is distinct from Dedicated Physical Control Channel (DPCCH) power reduction based on a command received in a closed loop power procedure; and 
 the occurrence of the congestion indication comprises receiving a transmit power control (TPC) DOWN command at approximately the same time as a retransmission rate of the E-DCH exceeds a predetermined threshold. 
 
 
     
     
       2. The wireless terminal of  claim 1 , wherein the congestion controller is configured to make a determination of an end of the congestion that prompted the congestion indication and to relax demand to lower the transport format combination upon the determination, the determination being made by at least one of:
 receipt of an end-of-congestion signal from the base station node; 
 expiration of a specified congestion time duration, the specified congestion time duration being either preconfigured at the congestion controller or signaled by the base station node. 
 
     
     
       3. The wireless terminal of  claim 1 , wherein the congestion indication comprises either (1) a predetermined number of transmit power control (TPC) DOWN commands received in a given time period or (2) a predetermined pattern of transmit power control (TPC) DOWN commands. 
     
     
       4. The wireless terminal of  claim 1 , wherein the congestion controller is configured to lower a previous transport format combination by a specified number of steps to obtain an updated transport format combination for transmitting the enhanced dedicated uplink channel (E-DCH) over the radio interface to the base station, and wherein the specified number of steps is preconfigured or signaled to the wireless terminal by the network. 
     
     
       5. The wireless terminal of  claim 1 , wherein the congestion controller is configured to determine an updated transport format combination in accordance with a specified maximum allowed uplink transmission power by selecting an updated transport format combination which maximizes E-DCH power and also fulfills a condition that total required power for the uplink is lower than a specified maximum allowed uplink transmission power. 
     
     
       6. The wireless terminal of  claim 5 , wherein the congestion controller is configured to determine the specified maximum allowed uplink transmission power by subtracting a power decrease value from an old uplink transmission power limit. 
     
     
       7. The wireless terminal of  claim 1 , wherein the congestion controller is configured to determine an updated transport format combination by:
 subtracting a requested uplink transmission power reduction value from a power value afforded a previous transport format combination to obtain a power limit for a new transport format combination; 
 using the new power limit to determine the new transport format combination. 
 
     
     
       8. A method of operating a wireless terminal comprising:
 obtaining a congestion indication over a radio interface with a base station; 
 in response to the congestion indication, reducing uplink transmission power of the wireless terminal by performing an expedited transport format combination reduction procedure comprising lowering a transport format combination for use by the wireless terminal for transmitting an enhanced dedicated uplink channel (E-DCH) over the radio interface to the base station; 
 wherein:
 the expedited transport format combination reduction procedure is distinct from Dedicated Physical Control Channel (DPCCH) power reduction based on a command received in a closed loop power procedure; and 
 obtaining the congestion indication comprises receiving a transmit power control (TPC) DOWN command at approximately the same time as a retransmission rate of the E-DCH exceeds a predetermined threshold. 
 
 
     
     
       9. The method of  claim 8 , further comprising:
 determining an end of the congestion that prompted the congestion indication by at least one of:
 receipt of an end-of-congestion signal from the base station node; 
 expiration of a specified congestion time duration, the specified congestion time duration being either preconfigured at the congestion controller or signaled by the base station node; and 
 
 relaxing a demand to lower the transport format combination. 
 
     
     
       10. The method of  claim 8 , wherein the congestion indication comprises either (1) a predetermined number of transmit power control (TPC) DOWN commands received in a given time period or (2) a predetermined pattern of transmit power control (TPC) DOWN commands. 
     
     
       11. The method of  claim 8 , further comprising lowering a previous transport format combination by a specified number of steps to obtain an updated transport format combination for transmitting the enhanced dedicated uplink channel (E-DCH) over the radio interface to the base station, and wherein the specified number of steps is preconfigured or signaled to the wireless terminal by the network. 
     
     
       12. The method of  claim 8 , further comprising determining an updated transport format combination by selecting an updated transport format combination which maximizes E-DCH power and also fulfills a condition that total required power for the uplink is lower than a specified maximum allowed uplink transmission power. 
     
     
       13. The method of  claim 12 , further comprising determining the specified maximum allowed uplink transmission power by subtracting a power decrease value from an old uplink transmission power limit. 
     
     
       14. The method of  claim 13 , further comprising determining the power decrease value by accumulating plural total power control commands over a transport format combination selection interval. 
     
     
       15. The method of  claim 13 , further comprising receiving the power decrease value in a signal from the base station. 
     
     
       16. The method of  claim 8 , further comprising determining an updated transport format combination by:
 subtracting a requested uplink transmission power reduction value from a power value afforded a previous transport format combination to obtain a power limit for a new transport format combination; 
 using the new power limit to determine the new transport format combination.